1. Field of the Invention
This invention relates to package substrates, and, more particularly, to a package substrate having a through hole, and a method of fabricating the same.
2. Description of Related Art
With the rapid development of semiconductor packaging technology, modern semiconductor devices come in a variety of forms. In order to enhance electrical functionality, passive components are installed on a surface of a package substrate. The passive components are electrically connected via a circuit layer to a semiconductor chip. However, the passive components occupy too much a layout area on the surface of the package substrate. Thus, such a package does not have good enough electrical functionality. To address the problem, manufacturers develop a modern package that has passive components embedded in the package substrate. Accordingly, the package substrate may have a greater layout area on its surface.
FIGS. 1 and 1′ show a package substrate 1 according to the prior art. The package substrate 1 includes a core board 10 having a through hole 100, a circuit layer 11 formed on the core board 10, and a metallic layer 12 formed on the core board 10 that surrounds a contour of the through hole 100.
In order to improve alignment precision, the metallic ring 100 is used as a predetermined region for a laser drilling process. After the through hole 100 is formed within the metallic ring 12, a passive component 4 having positive electrodes 40 and negative electrodes 41 formed on two opposite sides thereof, is installed in the through hole 100.
However, in the package substrate 1, since the metallic ring 12 has an inner contour equal to the contour of the through hole 100, when the passive component 4 is installed in the through hole 100, both the positive electrodes 40 and the negative electrodes 41 of the passive component 4 are likely to prop against side walls of the through hole 100, if the passive component 4 is deviated from a desired position. As a result, the positive electrodes 40 and the negative electrodes 41 of the passive component 4 are in contact with the metallic ring 12, as shown in FIG. 1′, thereby resulting in a short circuit for the passive component 4.
Therefore, how to avoid the short circuit from occurrence is becoming one of the most popular issues in the art.